In general, a known engine rotational speed controlling apparatus used to control an engine rotational speed of a heavy construction equipment such as an excavator is shown in FIG. 1.
According to the known engine rotational speed controlling apparatus, an operator controls a control dial 1 manually in order to control a rotational speed of an engine 4.
The control dial 1 is electrically connected with an equipment control unit (MCU) 2 and an engine control unit (ECU) 3 therein to transfer a value controlled by the operator to the engine 4.
In this case, the known machine control unit 2 wholly controls various driving devices required to drive the construction equipment and the engine control unit 3 controls driving of the engine among various driving devices of the construction equipment. Further, the control dial 1 converts a value inputted by the operator into a voltage value and transfers the converted voltage value to the machine control unit 2.
Accordingly, in the known engine rotational speed controlling apparatus, when the operator controls the control dial 1, the machine control unit 2 gives a command to the engine control unit 3 by receiving the corresponding voltage value and controls the engine rotational speed as high as a value controlling the control dial 1 to drive the engine 4.
However, in the known engine rotational speed controlling apparatus, when the control dial 1 or the machine control unit 2 are defective, an operation for the engine rotational speed cannot be normally controlled, and as a result, there is inconvenience in that the operator cannot control until the operator changes the control dial 1 or the machine control unit 2.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.